Transfer image process utilizing an organic phosphine as silver halide solvent

ABSTRACT

ORGANIC DERIVATIVES OF THE TRIHYDRIDES OF TRIVALENT ELEMENTS IN GROUP V-A OF THE PERIODIC TABLE HAVING AN ATOMIC NUMBER GREATER THAN 7 AND LESS THAN 83 ARE USED AS SILVER HALIDE SOLVENTS IN PHOTOGRAPHIC PROCESSING COMPOSITIONS. SPECIFICALLY, ORGANIC PHOSPHINES, ARSINES, STIBINES AND MIXTURES THEREOF ARE USED IN PHOTOGRAPHIC PROCESSING COMPOSITIONS WHICH FIND PARTICULAR UTILITY IN SILVER DIFFUSION TRANSFER TECHNIQUES.

United States Patent 3,578,449 TRANSFER IMAGE PROCESS UTILIZING AN ORGANIC PHOSPHINE AS SILVER HALIDE SOLVENT Stanley M. Bloom, Waban, Mass., assignor to Polaroid Corporation, Cambridge, Mass. N0 Drawing. Filed Jan. 22, 1968, Ser. No. 699,300

Int. Cl. G03c 5/54 US. CI. 96-29 Claims ABSTRACT OF THE DISCLOSURE Organic derivatives of the trihydrides of trivalent elements in Group V-A of the Periodic Table having an atomic number greater than 7 and less than 83 are used as silver halide solvents in photographic processing compositions. Specifically, organic phosphines, arsines, stibines and mixtures thereof are used in photographic processing compositions which find particular utility in silver diffusion transfer techniques.

BACKGROUND OF THE INVENTION The present invention relates to photography and, more particularly, is concerned with photographic compositions and processes.

In a typical dilfusion transfer photographic process, an aqueous composition containing a silver halide solvent is applied to a photoexposed silver halide emulsion stratum and a silver-receiving stratum which are maintained in superimposed relation for at least a portion of the developing period. In the emulsion stratum the developing agent reduces the exposed silver halide to silver, and concurrently therewith, the silver halide solvent reacts with unexposed silver halide to form a water-soluble complex silver salt which is transferred by diffusion to the silverreceiving stratum where it forms a visible image.

Though numerous silver halide solvents are known, those heretofore employed have suffered various drawbacks. Some solvents, such as the sulfites, are effective only with silver chloride and other solvents, such as the alkali metal cyanides, are too poisonous to be practical. In diffusion transfer processes, solvents such as ammonia and certain amines may act as weak solvents while the thiosulfates leave a harmful sulfur residue on the transfer image.

Besides their individual disadvantages, many silver halide solvents are eifective in Land diffusion transfer processes only under alkaline conditions so that highly alkaline media having a pH of at least 10 and usually higher are employed. As a consequence, the compositions must be stored in an air-tight container, and care must be taken to prevent prolonged exposure of the solution to air during packaging and use. Otherwise, atmospheric carbon dioxide will lower the pH of the composition to a point where it tends to lose its effectiveness. Such highly alkaline solutions, in addition to their instability in air, are often objected to for use in photographic procedures where the materials being developed and fixed are handled manually and may come into contact with the skin.

SUMMARY OF THE INVENTION The primary object of the present invention is to provide silver halide solvents that are free from many of the disadvantages associated with those solvents previously used and to provide compositions and processes employing said solvents.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises processes involving the several steps and the relation and order of one or 3,578,449 Patented May 11, 1971 more of such steps with respect to each of the others, and the compositions and products possess-ing the features, properties and the relation of elements which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

It has now been discovered that organic derivatives of the trihydrides of Group V-A elements having an atomic number greater than 7 and less and 83 exhibit unexpected properties as silver halide solvents for use in photographic processing compositions. Such compounds are effective with the different silver halides and mixtures thereof commonly used in photosensitive emulsions; may be used in either aqueous or organic solution to form soluble, diffusible complex silver salts; and produce good transfer images. Most important, the compounds of the present invention are oxidized in air to give a pale or colorless residue which is not deleterious to the transfer image and are effective complexing agents under less alkaline conditions than normally employed. The aliphatic derivatives of said elements, particularly, are readily oxidized in air and especially in the presence of alkali.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred organic derivatives of Group V-A elements to be employed in accordance with the present invention include primary, secondary and tertiary organic phosphines, arsines and stibines as represented by the following general formula wherein X is a member selected from the group consisting of P, As+ and Sb+ R are individually selected from the group consisting of hydrogen and a monovalent organic radical; m is a whole number 0 or 1, and not more than two of said R are hydrogen when m is 0; Y represents a group having the formula wherein Z is a divalent organic radical; and X and R are defined as above.

Since it is believed that the unshared pair of electrons of the Group V-A element is responsible for complexing the silver halide, monovalent organic radicals, broadly, are useful as the R groups of the compounds employed in the present invention. As used herein, monovalent organic radical is intended to include both cyclic and acyclic organic radicals whether homogeneous or heterogeneous in nature. Typical of radicals useful as the R moiety are alkyl, substituted and unsubstituted; cycloalkyl, substituted and unsubstituted; alkenyl, substituted and unsubstituted; cycloalkenyl, substituted and unsubstituted; aryl, substituted and unsubstituted; and

Generally, the substituents of the substituted monovalent organic radicals are solubilizing groups, i.e., groups selected to make the compound soluble in the particular liquid vehicle used. Typical of such substituents are SO H, OH, and COOH, particularly where the liquid vehicle is aqueous. Among other substituents that may be present, if desired, are halo, nitro, cyano, mercapto, amino, alkenyl, alkyl and alkoxy. Preferred R radicals are electron rich groups, i.e., groups with negative sigma (a) constants as defined by the Hammett 3 Equation (Physical Organic Chemistry, L. P. Hammett, McGraw-Hill, 1940, p. 256) and examplified by the mentioned above.

As with the monovalent organic radical, divalent or ganic radicals, generally, may comprise the Z- component of the compounds used in accordance with the present invention. Typical of the preferred radicals that may comprise the Z- component are arylene and groups represented by the formula (CR wherein q equals a whole number 1 to 3, inclusive.

Of the compounds suitable for use in the present invention, the organic phosphines and arsines are preferred and especially the organic phosphines because of their high affinity for silver ion.

Typical compounds corresponding to the foregoing general formula include:

Gi C

triphenylstiblne H5 2--Slb C 2115 triethylstibine HnCs-AS-CBHU di-n-octylarsine H-AS- 0 H2 C 6E5 benzylarsine H 0 2-As C 2H trlethylarslne triphenylarslne trls-(ortho-hydroxyphenyl)phosphine N,N-dlethauolaminodiphenylphosphine ortho-dimethylphosphinophenylenedimethylarslne CH3P (CHzCHzC O OH)2 bis (fi-carboxyethybmethylphosphine 2,3'bis (dimethylphosphino)-N,N,N-trimethylanilinium bisulfate In formulating photographic processing compositions utilizing the above-described compounds, the organic phosphine(s), arsine(s) and stibines(s) may be used singly or in admixture with each other. The total amount of the compounds(s) used may vary widely with the quantity added to the processing composition being sufiicient to give a satisfactory transfer print under the particular processing conditions employed. Ordinarily, the total quantity of these compound(s) incorporated into such compositions ranges between about 1 and 25% by weight of the processing composition.

Because the unshared pair of electrons of the Group V-A element is available under acid, neutral and alkaline conditions, the processing compositions formulated may vary from acid to very alkaline, e.g., from a hydrogen ion concentration of l N to a hydroxyl ion concentration of 5 N. Examples of bases capable of imparting the desired alkalinityl to the processing compositions are alkali metal hydroxides, such as sodium and potassium hydroxide, and amines, such as diethylamine and allylamine. Examples of acids capable of imparting the desired acidity include inorganic acids, such as hydrochloric and nitric acids and organic acids, such as citric and acetic acids. If desired, a suitable buffer system may be employed to maintain the pH of the composition within a predetermined range.

A composition embodying the present invention is broadly useful in a variety of photographic processes of the type in which silver complexes are formed from the unreduced silver halide of a photoexposed and at least partially developed silver halide stratum. The silver complexes formed should be soluble in the liquid vehicle of the composition which is usually water but it may be an organic liquid, preferably a volatile organic liquid, or a mixture of water and an organic liquid. Illustrative of organic liquids that may be employed are alcohols, e.g., methanol; ethers, e.g., diisopropyl ether; ketones, e.g., acetone; and aromatic solvents, e.g., toluene.

A composition embodying the present invention specifically suitable for use in the production of transfer images comprises, in addition to complexing agents of the above-described type, a suitable silver halide developing agent. Among the developing agents commonly used are benzene and naphthalene compounds having hydroxy or amino substituents ortho or para to one another, e.g., hydroquinone, chlorohydroquinone, bromohydroquinone, toluhydroquinone, Metol (p-methyl aminophenol sulfate), glycin (p-hydroxyphenylaminoacetic acid), pyrocatechin, pyrogallol and bis-N,N-methoxyethyl hydroxylamine.

In one such transfer process, the processing solution is applied in a uniformly thin layer between the superposed surfaces of a photoexposed gelatino silver halide element and an image-receiving element, for example, by advancing the elements between a pair of pressure-applying rollers. The elements are maintained in superposed relation for a predetermined period, preferably for a duration of to 120 seconds, during which exposed silver halide is reduced to silver and unreduced silver halide forms a water-soluble, complex salt which diffuses through the layer of solution to the image-receiving element, there to be reduced to an argental image. At the end of this period, the silver halide element is separated from the imagereceiving element. Materials useful in such a transfer process are described in US. Pat. No. 2,543,181, issued in the name of Edwin H. Land on Feb. 27, 1951, and in numerous other patents.

The silver halide element may be any of those conventionally used in silver diffusion transfer processes and generally comprises a silver halide emulsion carried on a base, e.g., glass, paper or plastic film. The silver halide may be a silver chloride, iodide, bromide, iodobromide, chlorobromide, etc. The binder for the halide, though usually gelatin, may be a suitable polymer such as polyvinyl alcohol, polyvinyl pyrrolidone and their copoymers.

The image-receiving element preferably includes certain materials, the presence of which, during the transfer process has a desirable effect on the amount and character of silver precipitated on the image-receiving element. Materials of this type are specifically described in U.S. Pat. Nos. 2,690,237 and 2,698,245, both issued in the name of Edwin H. Land on Dec. 28, 1954.

Separating of the silver halide element from the imagereceiving element may be controlled so that the layer of processing composition is removed from the imagereceiving element or the layer of processing composition is caused to remain in contact with the image-receiving element, e.g., to provide it with a protective coating. Techniques which enable such results to be accomplished as desired are described in US. Pat. No. 2,647,056 issued to Edwin H. Land on July 28, 1953. In general, the processing reagents are selected so that traces remaining after the solidified processing layer has been separated from the silver image or which remain in said layer adhered as a protective coating on the silver image, as indicated above, are colorless or pale, so as not to appreciably affect the appearance of the image and to have little or no tendency to adversely react with the silver image.

As indicated above, a unique and most desirable property possessed by the silver solvents of the present invention is their ability to be readily oxidized in air to a stable residue which has no tendency to react with the silver of the transfer image. The residue, besides being non-reactive with the argental image, is pale or colorless and thus, has little or no tendency to obscure the image.

The following examples are given to further illustrate the present invention and are not intended to limit the scope thereof.

EXAMPLE 1 A photosensitive element having a gelatino silver iodobromide emulsion on film base was exposed to a step wedge and then processed by spreading a layer of processing composition approximately mils thick between the thus-exposed emulsion and a superposed image-receiving element comprising a stratum of regenerated cellulose containing colloidal nickel sulfide as the silver precipitant. The processing composition comprised:

Water-10 cc.

Hydroxyethyl cellulose-5.0 g.

Zinc acetatel.5 g.

Cesium hydroxide-4.47 g. Bis-N,N-methoxyethyl hydroxylamine0.5 cc. Gum arabic2.3 g.

Tris- (para-hydroxyphenyl)phosphine-0.4 g.

After an imbibition period of 120 seconds, the imagereceiving and photosensitive elements were separated to reveal a good image of moderate contrast on the imagereceiving sheet.

Images of moderate contrast also were obtained with formulations similar to the foregoing except that the tris- (para-hydroxyphenyl)phosphine was used in amounts of 0.2, 0.3, 0.6 and 0.8 gram, respectively.

EXAMPLES 2-4 Water10 cc.

Triethanolamine-0.56 g.

Hydroxyethyl cellulose-5.0 g.

Zinc acetate1.5 g.

Thiazolidinethione-0.00 1 5 g.

Potassium hydroxide-1.5 g. Bis-N,N-methoxyethylhydroxy1amine0.5 cc.

The silver halide solvent(s) added to the base formulation for each of the Examples 2-4 is given in Table I below.

After an imbibition period of 60 seconds, the image receiving and photosensitive elements of each of the examples were separated to reveal good images of good contrast. A measurement of the maximum density of each of the resulting negatives showed that the addition of an organic phosphine to the uracil improved density. The densities obtained are given in the following table.

TABLE Tris- (parahydroxyphenyl) Example Uracil phosphine No. (grams) (grams) Dmax In preparing the foregoing compositions, the hydroxyethyl cellulose and the respective hydroxides were dissolved in water at room temperature and the remaining ingredients added with stirring until dissolved.

As indicated above, the organic phosphines, arsines, stibines and mixtures thereof capable of reacting with a silver halide to form a complex silver salt soluble in the liquid medium employed are useful in both conventional and diffusion transfer processes and, as illustrated, may be used in conjunction with another silver halide solvent. Also, the processing composition may include preservatives or other components commonly used in the art and may be modified by the substitution of ingredients for those specifically mentioned.

Since certain changes may be made in the above compositions and processes without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A photographic processing composition comprising a liquid vehicle having dissolved therein, a silver halide developing agent and, as a silver halide solvent, at least one compound represented by the formula wherein X is a member selected from the group consisting of P, As+ and Sb+ R are individually selected from the group consisting of hydrogen and a monovalent organic radical; m is a whole number 0 or 1, and not more than two of said R are hydrogen when m is 0; Y represents a group having the formula Z-XR wherein Z is a divalent organic radical; and X and R are defined as above, said compound being capable of reacting with silver halide to form a complex silver salt that is soluble in said vehicle.

2. A photographic processing composition according to claim 1 wherein said vehicle is a volatile organic liquid.

3. A photographic processing composition according to claim 1 wherein said vehicle is water.

4. A photographic processing composition according to claim 3 which ranges from a hydrogen ion concentration of 1 N to a hydroxyl ion concentration of 5 N.

5. A photographic processing composition according to claim 4 wherein said compound is tris-(para-hydroxyphenyl)phosphine.

6. A photographic method comprising the steps of (1) reacting exposed silver halide of a photosensitive silver halide emulsion with a silver halide developing agent in solution in a liquid vehicle,

(2) reacting unreduced silver halide of said photosensitive emulsion with a compound represented by the formula:

wherein X is a member selected from the group consisting of P, As+ and Sb' R are individually selected from the group consisting of hydrogen and a monovalent organic radical; m is a whole number 0 or 1, and not more than two of said R are hydro- 8 gen when m is 0; Y represents a group having the formula -ZXR wherein Z is a divalent organic radical; and X and R are defined as above, said compound 'being capable of reacting with silver halide to form a complex silver salt thatis soluble in said vehicle,

(3) transferring said complex silver salt to a superposed image-receiying layer and (4) reducing said transferred complex silver salt to provide a silver image.

7. A photographic method according to claim 6 wherein said liquid vehicle is a volatile organic liquid.

8. A photographic method according to claim 7 wherein said liquid vehicle is water.

9. A photographic method according to claim 8 wherein said vehicle ranges from a hydrogen ion concentration of 1 N to a hydroxyl ion concentration of 5 N.

10. A photographic method according to claim 1 Wherein said compound is tri-(para-hydroxyphenyl)phosphine.

References Cited UNITED STATES PATENTS 1/1961 Land 96-3 NORMAN G. TORCHIN, Primary Examiner W. H. LOUIE, JR., Assistant Examiner US. Cl. X.R. 96-66 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 57 q 2 -q Dated May 11, 1971 Inventor( Stanlev M. Bloom It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 4, line 17, CH

I 3 H C\ /CH H C-I' I Q P 50 should P 3 C CH3 read as 31- H H H C--N 3C\P/C 3 Hso 3 H C CH Column 4, line 27, "compounds (s) should read as --compound (5) Column 4, line 40, "alkalinityl" should read as -alkalinity-.

Column 7, line 28, after "Sb" insert --+3 Column 8, line 14, after claim delete "7" and insert -6-.

Column 8, line 19 after claim delete "l" and insert 9.

Signed and sealed this 28th day of December 1971.

(SEAL) Attest:

EDWARD M.FIEICHER,J'R. ROBERT GOTTSCHALK Attesting Officer Acting Commissioner of Patents 

